She is always open-hearted about her thoughts, which makes her friends feel close to her.

open-hearted 是由形容词 open（开放的）和名词 heart（心）加上后缀 -ed 组成的复合形容词。open 表示"不封闭的、坦率的"，heart 在这里象征"情感、内心"。open-hearted 字面意思是"敞开心扉的"，引申为"坦率的、真诚的"。